Advice? Help? Anyone have a difficult parent or in-law?

Hi friends.  I could use some advice, counseling, a kind ear to listen, or maybe just some words of understanding.  I am in such a difficult place with my mother, and it's really hard right now.

I've written about my mother before, and I probably will again.  She is an incredibly difficult woman.  She's manipulative, controlling, melodramatic, and very egocentric.  On top of that, she is incredibly oversensitive and arrogant.  She's difficult to be around for long periods of time (well, even for short periods of time), and she's impossible to talk to about anything except what she absolutely agrees with.  She is great at dishing out opinions and criticism, but can't take even the slightest bit of disagreement or criticism herself, no matter how constructive.  Even when someone with a golden tongue seems to get through to her in the moment, the next time I talk to her, after she's had time to mull over what they've said, she's turned it all around and made herself the righteous winner and the other person the jerk.  EVERY. SINGLE. TIME.

To make matters worse, she doesn't eat well or take care of herself physically, and is in extremely poor physical health, which makes her believe everyone owes it to her to come over and take care of anything and everything - cleaning litter boxes, basic housecleaning, big projects - you name it, she believes someone else should do it.

My brother and sister-in-law moved away primarily to get away from her.  All of her friends are ten years older than she is and just as opinionated and difficult as she is (I don't know how they all get along!).  She was an only child, my father passed away 8 years ago, her parents are both gone, and she is basically estranged from most of her extended family, none of whom live anywhere nearby in any case.  So she has attached herself to me, and now especially my children, digging in her fingernails as hard as she can for fear of being set adrift.  Unfortunately, the neediness is really starting to get me down, since I have two 3-year-olds who legitimately need me.  The tighter she squeezes, the more I feel like I'm being strangled.

I could go on and on.  I could tell you stories of how she would buy gifts for me to give my friends for Christmas when I was in high school, and she'd wrap them first so even I wouldn't know what they were (?!?!).  How when I got my first bank account with an ATM card before leaving for college, she watched me enter my pin, then announced in the car that she knew what my secret code was - like she wanted to make SURE that I knew she was the one in control.  How when I worked at a movie theater for a summer during college and an old high school friend asked if she and her mom could come to a free movie, my mother told me she would never speak to me again if I allowed it, since she didn't like my friend's mom.  How she was so angry after my half-sister didn't come to my father's funeral (it's a long complicated story with a lot of misunderstandings), she asked my husband to not allow my sister to visit his family in Italy when she took a European trip YEARS LATER.

Every once in a while, my mom goes on a depressive binge and calls me constantly (well, even more constantly than usual), saying that she doesn't know if she'll make it another day, etc. etc. (I've heard it all before), and sometimes, like now, she accuses me of keeping my kids from her (when I don't want to visit more than once a week) and says that the kids are the only thing that makes her happy.  She says a lot of other accusatory things as well.  And trust me, I DO know that her problems and unhappiness are not my fault, but the constant bombardment is just getting me down (she called 5 times today, and that is relatively tame).

When my husband and I were first dating, she left a note that seemed suspiciously like a suicide note (it was vague enough that it could be interpreted in other ways, she later claimed she was just leaving to go on vacation) and disappeared, so my brother called the police, who caught up with her at my dad's nursing home and took her for psychiatric evaluation.  They let her go a few hours later, according to her because nothing was wrong with her.  I was terrified my now-husband would drop me like a hot potato after seeing the crazy he was marrying into.  My mom has seen a psychologist, too, who apparently (according to her, I've never spoken to him) says that there is nothing wrong with her, but that the real problem is her children.  I don't doubt that she has some depression, but I can't stand the way she uses it, threatening suicide when she doesn't get her way or when she feels like she's not getting enough attention, but then claiming nothing is wrong when I say she needs psychiatric help.

Basically, I'm tired of dealing with an extra toddler.  (Like I just said to my husband, if I had a dollar for every time my mother has said she has a big favor to ask of me, well, he could quit his job).

I just don't know what to do anymore.  I dread spending time with her, I dread talking on the phone with her.  It's impossible to have a reasonable conversation since I disagree with almost everything that comes out of her mouth, but she takes my silence as acceptance.  If I don't answer the phone, she calls again and again and again, but she refuses to leave a message with any real information about why she's calling.  I'm so tired of dealing with it all, and I feel like it's never going to stop.  I'm tempted to move farther away just so I don't have to keep making up excuses to not visit.

And here's the thing, all the reasonable-sounding things you'll suggest won't work.  She cannot be changed, this I know, and there is no way to talk to her rationally about any of this.  Trust me, I've tried, and many people in my life who originally advocated trying to work things out with her have admitted defeat.  It's more like how do I train myself to handle it better?  I would love, in some ways, to just cut her out of my life, but I don't think my conscience can handle it, so what else can I do?